The present disclosure relates to a hydraulic control unit comprising a device and to a method for measuring a fluid pressure and for verifying the fluid pressure that has been measured.
Devices for measuring a fluid pressure are used in many areas. For example, in the case of a hydraulic vehicle brake, an electronic control unit (ECU) drives an extremely wide variety of components, such as valves, depending on the pressure which is measured by the device in the fluid channels. Pressure sensors for measuring the fluid pressure often have a piezoresistive element, the resistance of said piezoresistive element changing in the event of deformation and said piezoresistive element being part of a resistance measurement bridge. A measure of the fluid pressure is then a voltage difference between the voltage dividers of the resistance measurement bridge. The voltage difference which is measured is then usually passed on for the purpose of further processing, and the signal which has been further processed is supplied to the electronic control unit.
In known solutions, additional components are used for verifying fault-free functioning of the resistance measurement bridge and the subsequent signal processing, said additional components resulting in additional costs. In addition, the additional components which serve for verifying the pressure measurement reduce the reliability of the components which serve for the actual pressure measurement since more complex structures are used for the resistance measurement bridge and the subsequent signal processing.
WO 97/27802 A discloses a device for measuring pressure, temperature and throughflow, which device is intended particularly for use in the medical field, such as for intracoronary pressure measurement for example. A circuit arrangement has two resistance measurement bridges. The first resistance measurement bridge is intended for throughflow measurement and for temperature compensation, and the second resistance measurement bridge is intended for pressure measurement. For the purpose of temperature compensation, the second resistance measurement bridge is calibrated before the actual measurement operation by the potential difference between points A and B being recorded as a function of the potential difference between points A and C at known temperatures. This previously determined calibration curve can then be used to determine an offset value by which the signal that has been measured in the actual measurement operation and is representative of the pressure is increased or reduced depending on the temperature.
DE 103 04 024 A1 discloses a method and a circuit arrangement for checking a pressure sensor arrangement in an electronically controlled motor vehicle brake system. The sensor arrangement has a resistance measurement bridge which is connected to an electrical evaluation circuit. A fault identification method is carried out in the electrical evaluation circuit by comparing the electrical output signals with setpoint values and comparison values.
U.S. Pat. No. 5,343,755 B discloses a pressure sensor comprising a resistance measurement bridge which generates a pressure-dependent transverse bridge voltage. The pressure sensor further has a resistance element which is electrically connected to the resistance measurement bridge and also to an amplifier for amplifying the temperature-dependent voltage drop at the resistance element.
EP 1 087 219 A2 discloses a pressure sensor comprising a resistance measurement bridge and a voltage divider which is connected in parallel to the resistance measurement bridge. The resistance measurement bridge is arranged on a diaphragm of a silicon substrate. The transverse bridge voltage of the resistance measurement bridge is representative of the pressure which acts on the diaphragm. Furthermore, a differential voltage between the resistance measurement bridge and the voltage divider is used to draw a conclusion about a possible malfunction of the resistance measurement bridge.